There has been known a valve timing control device as disclosed in Patent Document 1 cited below. Patent Document 1 discloses a device for varying the phase angle of the camshaft 1 of an internal combustion engine relative to the drive plate 2 driven by the crankshaft of the engine, in the phase advancing direction (which is the same as the rotational direction of the driving plate 2) or phase retarding direction (which is opposite to the rotational direction of the driving plate 2) to vary valve timing by means of a cam (or camshaft 1).
In the device of Patent Document 1, the driving plate 2 is mounted rotatable relative to a lever shaft 13 which is fixedly coupled to a spacer 8. The lever shaft 13 has three levers 12 each of which is pivotally connected at one end thereof to one end of a link arm 14. The other end of the link arm 14 is in turn pivotally connected to a movable member 11 which can slide in a generally radial guide slit 10 formed in the front face of the driving plate 2. As the movable member 11 slides in the radially inward direction, the phase angle of the camshaft 1 is varied relative to the driving plate 2 through the rotation of the link arm 14 about a pin 16. While, when the movable member 11 slides in the radially outward direction, the link arm 14 is rotated in the opposite direction, thereby returning the phase angle of the camshaft 1.
Arranged ahead of the movable member 11 is a guide plate 24 (rotary drum) which is rotatable relative to the camshaft 1 (lever shaft 13) and drive plate 2. Rotatably supported between the recess 21 formed in the front end of the movable member 11 and spiral grooves (spiral guides) 28 formed in the rear end of the guide plate 24 are balls 22 that can roll between them. In response to the rolling motions of the balls 22 in the spiral grooves 28, the movable member 11 slides in the generally radial guide slit 10 in the radially inward or outward direction depending on the relative motion of the guide plate 24 relative to the drive plate 2.
The guide plate 24 can be rotated in the phase retarding direction relative to the drive plate 2 by the braking force of a first electromagnetic brake 26, but can be rotated in the phase advancing direction relative to the drive plate 2 by a planetary gear mechanism (reverse rotary mechanism) 25 operated by a second electromagnetic brake 27, as stated below.
The planetary gear mechanism (reverse rotary mechanism) 25 has a sun gear 30 provided on the rear end of a braking flange 34 that is rotatably mounted on the camshaft 1 (lever shaft 13) ahead of the guide plate 24, and a ring gear 31 provided on the front end of the guide plate 24. Further, the planetary gear mechanism 25 has a multiplicity of planetary gears 33 that are supported to engage the sun gear and ring gear 31 such that the gears 33 are rotatable relative to a carrier plate 32 fixed to the lever shaft 13. As the brake flange 34 is braked by the second electromagnetic brake 27, causing the planetary gears 33 to be rotated, the ring gear 31 is accelerated in the phase advancing direction, so that the guide plate 24 is rotated in the phase advancing direction relative to the drive plate 2.
In short, the device of Patent Document 1 is adapted to rotate the guide plate 24 relative to the drive plate 2 by a pair of electromagnetic brakes (26 and 27) and a planetary gear mechanism (reverse rotary mechanism) 25 and change the phase angle between the camshaft 1 and the crankshaft (drive plate 2) in accordance with the direction of the relative rotation.    Patent Document 1: JPA Laid Open 2006-77779